Finally found a site I've been looking for all morning...

This is a spoiler heavy site, but it'll help understand the Type-Moon universe, especially helpful in understanding what's going on in Tsukihime...

http://www.geocities.com/max3075/top.htm

This page specifically gives what it seems like a good intro into Fata/stay night

http://www.geocities.com/max3075/fate/index.htm